1. Field of the Invention
The present invention relates to a device and method for preventing flicker that occurs while displaying image data and a computer-readable recording medium on which a program for flicker prevention is recorded.
2. Description of the Related Art
In display devices such as television receivers and computer monitors, image data is displayed according to an interlace scheme. The interlace scheme is a technique of alternately displaying odd numbered scanning lines and even-numbered horizontal scanning lines to display moving image data smoothly. The interlace scheme is used when a client computer receives image data stored in a World Wide Web server (hereinafter referred to as xe2x80x9cWeb serverxe2x80x9d) and displays it on such a display device.
However, flicker may occur when image data having strong color contrast or clear color boundaries, such as an artificially generated image data, is displayed according to the interlace scheme. An example of image data having clear color boundaries is artificially generated image data with a horizontally extending line having a width of one pixel. For example, where the interlace scheme is employed, this line appears only during the display of odd-numbered scanning lines. When displaying even-numbered scanning lines, the line will not appear. (And vice versa). This line is displayed in a flashing state and hence may cause a flicker.
Conventionally, to avoid such a flicker phenomenon, image data to be displayed may be limited to natural image data lack distinct color boundaries and are relatively weak in color contrast. Another conventional method is to subject image data in advance to, for example, a process of creating a gradient color boundaries and supply resulting image data to the display.
As described above, conventionally, image data to be displayed are restricted or color boundaries of image data are created a gradient color boundaries in advance to prevent flicker.
However, the following problems will occur if the above conventional flicker preventing methods are applied to a system of displaying an arbitrary image stored in a Web server using browser software in a client.
First, there may occur a case that image data stored in a Web server has not been subjected in advance to a process of creating a gradient color boundaries, in which case image data is displayed that may cause a flicker.
Second, even if image data stored in a Web server has been subjected in advance to a process of shading off color boundaries, the process may not be suitable for the client because the display device and environment vary from one client to another. In this case, there is a problem that the user on the client cannot make a correction because the process of shading off color boundaries is performed on the server.
Accordingly, the present invention is directed to a device and method for preventing flicker that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
In accordance with the purpose of the present invention, as embodied and broadly described, the present invention is directed to a device for preventing flicker which occurs when displaying image data. The device comprises a first converter, an orthogonal transforming unit, and a second attenuating unit, an inverse orthogonal transforming unit, and a second converter. The first converter converts image data into a first set of signals having at least one luminance signal and two color difference signals. The orthogonal transforming unit orthogonal transforms the first set of signals. The high-frequency attenuating unit attenuates a high-frequency portion of at least one of the orthogonal transformed signals. The inverse orthogonal transforming unit inverse orthogonal transforms the high-frequency attenuated set of signals into a second set of signals having at least one luminance signal and two color difference signals. The second converter converts the resultant second set of signals into image data for display.
Also in accordance with the present invention, there is provided a method for preventing flicker that occurs when displaying image data. The method comprises the steps of converting image data into a first set of signals having at least one luminance signal and two color difference signals, orthogonal transforming the first set of signals, attenuating a high-frequency portion of at least one of the orthogonal transformed signals, inverse orthogonal transforming the high-frequency attenuated set of signals into a second set of signals having at least one luminance signal and two color difference signals, and converting the resultant second set of signals into image data for display.
Also in accordance with the present invention, there is provided a computer-readable memory with instruction means for preventing flicker. The computer-readable memory comprises instruction means for causing a computer to convert image data into a first set of signals having at least one luminance signal and two color difference signals, instruction means for causing a computer to orthogonal transform the first set of signals, instruction means for causing a computer to attenuate a high-frequency portion of at least one of the orthogonal transformed signals, instruction means for causing a computer to inverse orthogonal transform the high-frequency attenuated set of signals into a second set of signals having at least one luminance signal and two color difference signals, and instruction means for causing a computer to convert the resultant second set of signals into image data for display.